'GL_PN_TRIANGLES_ATI' undeclared (first use of this function)
'GL_PN_TRIANGLES_POINT_MODE_ATI' undeclared (first use of this function)
'GL_PN_TRIANGLES_POINT_MODE_CUBIC_ATI' undeclared (first use of this function)
'GL_PN_TRIANGLES_TESSELLATION_LEVEL_ATI' undeclared (first use of this function)

The Mac glext.h declares the extension as GL_ATIX_pn_triangles, so all the symbols end with ATIX rather than ATI. Changing the code you posted earlier by replacing ATI with ATIX everywhere allowed it to compile.

If this is different from the PC version and you want the same code to work, you could always declare the functions and constants yourself: